Large-scale assessment of olfactory preferences and learning in Drosophila melanogaster: behavioral and genetic components.

Elisabetta Versace,Julia Reisenberger

doi:10.7717/peerj.1214

Abstract

In the Evolve and Resequence method (E&R), experimental evolution and genomics are combined to investigate evolutionary dynamics and the genotype-phenotype link. As other genomic approaches, this methods requires many replicates with large population sizes, which imposes severe restrictions on the analysis of behavioral phenotypes. Aiming to use E&R for investigating the evolution of behavior in Drosophila, we have developed a simple and effective method to assess spontaneous olfactory preferences and learning in large samples of fruit flies using a T-maze. We tested this procedure on (a) a large wild-caught population and (b) 11 isofemale lines of Drosophila melanogaster. Compared to previous methods, this procedure reduces the environmental noise and allows for the analysis of large population samples. Consistent with previous results, we show that flies have a preference for orange vs. apple odor. With our procedure wild-derived flies exhibit olfactory learning in the absence of previous laboratory selection. Furthermore, we find genetic differences in the olfactory learning with relatively high heritability. We propose this large-scale method as an effective tool for E&R and genome-wide association studies on olfactory preferences and learning.

Highlights

Ongoing evolutionary dynamics and genotype-phenotype mapping can be studied during experimental evolution through subsequent phenotyping and genomic sampling (Travisano & Lenski, 1996; Wiser, Ribeck & Lenski, 2013)
Aiming to use Evolve and Resequence (E&R) for investigating the evolution of behavior in fruit flies, we have developed a simple and effective method based on a T-maze to assess olfactory preferences and learning in large samples of fruit flies of both sexes as well as in smaller samples
We find evidence for olfactory preferences and learning in a large population of D. melanogaster originally caught in South Africa and in a population of inbred lines originally caught in Portugal

Summary

Introduction

Ongoing evolutionary dynamics and genotype-phenotype mapping can be studied during experimental evolution through subsequent phenotyping and genomic sampling (Travisano & Lenski, 1996; Wiser, Ribeck & Lenski, 2013) This method is known as Evolve and Resequence (E&R) (Turner et al, 2011) and can be applied to entire populations by sequencing at the same times hundreds of individuals (Pool-seq, see Futschik & Schlotterer, 2010) of the same population. Thanks to the advancements of high-throughput sequencing techniques, the E&R method has been used to track the changes in genomic composition across thousand of generations in bacteria (Wiser, Ribeck & Lenski, 2013) and in eukaryotes with a fast life cycle, such as yeast (Barrick & Lenski, 2013) and fruit flies (Schlotterer et al, 2015). Despite the success in identifying some causative genes (e.g., Zhou et al, 2011; Martins et al, 2014), theoretical (Schlotterer et al, 2015; Kofler & Schlotterer, 2014) and empirical evidence (Tobler et al, 2014; Franssen et al, 2015) has clarified that many of the significantly changed variants are false positives derived by short or long-distance linkage disequilibrium

Methods

Results

Conclusion